A. Technical Field
The present invention relates generally to the proper operation of telephone headsets and other communication devices. Specifically, the present invention relates to the identification of a voice signal from a microphone in a headset or communication device that is too weak and the subsequent notification of the weak signal to a user.
B. Background of the Invention
Communications headsets typically have a microphone positioned on an adjustable arm that allows a user to move the microphone to a desired position, which the user finds comfortable. However, the adjustable arm may also be mispositioned without the user's knowledge. This problem occurs most notably with users who have little experience and/or training in the proper use of communications headsets.
Effective use of a communications headset requires that the microphone be positioned within a particular distance from the user's mouth. The importance of properly positioning a microphone is amplified when high quality noise canceling microphone headsets are used. A mispositioned noise canceling microphone experiences a reduction of sensitivity to the user's voice, but its sensitivity to background noise remains the same. In either case, the microphone's signal to noise ratio (the ratio of the user's voice to ambient noise) decreases, thereby reducing the overall quality of the voice signal or rendering the voice signal unintelligible at the receiver side.
The use of a headset allows a user to perform other tasks while having a conversation. For example, telemarketers often use headsets because it allows the use of a computer during a conversation. Oftentimes, because of various distractions like the use of a computer during a conversation, a user does not talk loud enough to ensure a sufficient sound quality at the receiver side. As was the case with a mispositioned microphone, the user is unaware of the poor sound quality at the receiver side until the listener verbally indicates the problem.
Attempts to remedy poor sound quality have focused on reducing the signal to noise ratio at the receiver side. For example, U.S. Pat. No. 5,091,954, entitled “Noise Reducing Receiver Device,” (hereinafter Sasaki) uses a feedback mechanism on an amplifier in a telephone receiver to adjust the transfer function of the amplifier. The transfer function is shifted to remove ambient noise in the signal. However, Sasaki is designed for situations where the signal to noise ratio is above a specific level. If for example, the microphone is grossly mispositioned or the user is talking extremely quietly, then the signal may be too weak for the amplifier to function properly. As a result, a talker-side solution is required for a mispositioned microphone identification device.
U.S. Pat. No. 4,777,649, entitled “Acoustic Feedback Control of Microphone Positioning and Speaking Volume,” (hereinafter Carlson) describes an apparatus coupled to a telephone handset that will detect when a handset is either too close or too far from a user's mouth. Specifically, a circuit determines whether the handset is mispositioned using multiple comparators. A first comparator is used to determine whether the handset is too far by comparing a voice signal from a handset microphone to a first threshold. If the signal is weaker than the first threshold than the microphone is too far. A second comparator is used to determine whether the handset is too close by comparing a voice signal from the handset microphone to a second threshold. If the signal is strong than the second threshold than the microphone is too close. A switch is used to turn off the voice feedback into the handset speaker when the microphone is mispositioned, that is, when the signal is either below the first threshold or above the second. As a result, if the microphone is properly positioned then the user will hear his/her own voice in the handset speaker. However, if the microphone is mispositioned, the user will not hear his/her voice in the handset speaker.
Carlson's use of the user's own voice as the indication of whether the microphone is mispositioned results in inherently limited quality and reliability. For example, if Carlson's circuit were to malfunction, the handset itself would be almost inoperable because the user could not hear his/her voice in the handset speaker. Second, the notification directly interrupts the use of the handset which reduces the quality of the conversation because the handset's feedback into the earpiece may be activated multiple times during a conversation causing an uncontrollable distraction to the handset user. As mentioned above, these limitations are caused by the fact that Carlson does not detect speech levels below an audible threshold. As a result, there is a need for a mispositioned microphone identification device that senses when a user is actually speaking below an audible threshold so that a microphone misposition indication may be provided by a device not implementing the talker's actual voice (i.e., voice feedback).
Accordingly it is desirable to provide a microphone position and speech level sensor that operates on the talker-side and senses when a user is actually talking.
As described above, at least a portion of Carlson's circuit is embedded in the handset itself. Specifically, the voice feedback mechanism is operating within the earpiece and is inseparably coupled to the earpiece circuitry. As a result, a handset may not be upgraded to include Carlson's mispositioning circuitry; rather the entire handset must be replaced. This upgrade would be very expensive for companies who use a large number of handsets. For example, telemarketing companies require a large number of handsets or headsets and replacing all of these would be costly.
Accordingly, it is desirable to provide a microphone position and speech level sensor that may be used to upgrade pre-existing headsets or handsets.